The present invention relates to pneumatic tires and more particularly the bead rings for reinforcing the beads of such tires.
It is known to cover bead rings with a sheath made of rubber which is vulcanized, for instance, in the mold at the same time as the rest of the tire. Bead rings having such a sheath have the following drawbacks.
When the bead rings are formed of wires arranged side by side without being attached to each other, the poor mechanical resistance of the rubber sheaths does not permit sufficient cohesion of the bead rings, so that the transportation of them is difficult, since there is the danger of causing the deformation of the bead rings. Furthermore, the deformation of the rubber sheaths within the tires causes a deformation of the bead rings, with relative displacement of the wires of the bead rings, even if the bead rings were of a uniform geometrical shape at the time of the production of the tires. This geometrical instability leads to a heterogenous working of the wires, which causes damage to the beads which they reinforce. It has been attempted to avoid these drawbacks by assembling the wires together from place to place by means of collars, for instance metal collars, but such assembling is difficult and expensive to effect and it does not make it possible to avoid deformation of the bead rings in all cases.
When the bead rings are formed of wires which are held firmly together so as to form an assembly of a stable geometrical shape, this shape is frequently not adapted to the structure of the beads or to the stresses existing in the beads, and the rubber sheaths do not permit such an adaptation in shape as a result of the deformation of these sheaths.